| The transpiration stream is the route taken by water from the roots, through the xylem cells, and into the atmosphere through the stomata. Previously, it was shown that the transcription factor, AtMYB61, was both sufficient and necessary to control the diurnal changes in stomatal apertures. Here it is shown that AtMYB61 directly controls the two other major facets of the plant transpiration stream, xylem formation and root system architecture. AtMYB61 is expressed in differentiating xylem cells and in emerging lateral roots. Loss of AtMYB61 function decreases xylem formation, induces alterations in xylem cell structure and decreases lateral root formation, whereas, gain of AtMYB61 function has the opposite effect. The loss of AtMYB61 also results in several seed related traits, reinforcing the nature of this pleotropic transcription factor. AtMYB61 regulates a suite of downstream target genes, which themselves determine the extent and features of xylem cell formation and seed traits. AtMY.B61 is the first transcription factor that defines a genetic module that directly links all major components controlling the plant transpiration stream. |
